What are the risks with contrast media?

Iodine-based contrast media are generally safe. However, occasionally people have side effects such as an allergic reaction or kidney problems, which are generally temporary.

Allergic reactions to contrast media can occasionally be serious, so it’s essential you tell the health professional about any previous allergic reactions you’ve had, especially if you’ve had a previous reaction to contrast media.

The risk of kidney problems with contrast dye is greatest in people with pre-existing kidney problems and/or diabetes. However, some people may not know they have reduced kidney function — in general, your kidney function reduces as you age and some medicines (e.g. anti-inflammatory treatments for arthritis) may aggravate this. If there’s any doubt, your doctor should organise a blood test to check your kidney function before the scan.

Some medicines, such as metformin, which is used for diabetes, may increase the risk of kidney problems with contrast dye. To help avoid problems, you should tell the doctor and/or radiographer about all the medicines you are taking before the procedure, especially if you are over 70 years of age.

Very rarely, iodine-based contrast dyes can cause thyroid problems. The risk is greatest if you have a pre-existing problem relating to an overactive thyroid, such as Graves’ disease. If you have thyroid disease, discuss this with your doctor before your X-ray. In some instances it may not be possible to give you the contrast dye.

Because barium is not absorbed into the blood, allergic reactions with barium-based contrast media are extremely rare. The barium that is swallowed for a barium study will pass through the intestines and eventually be expelled in the bowel motions.

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